I've been in the process of recreating many synth sounds from an album to play in a live setting. There is this one sound that I am having trouble recreating.
I've spent many hours on this with no success. I've tried assigning a "guitar" LFO to the filter modulation as well as messed around with the "talking modulator" but am not able to get close to this sound.

What confuses me is that I am able to get pretty close to the effect by simply manually turning the cutoff knob on a simple 2 osc -(detuned saw - saw/pulse) patch. I figured assigning the AMS1 for filter A to an LFO would do the same thing but it does not sound the same. Am I missing something obvious?

If anyone has any suggestions on how to go about getting this effect I would be ever so gracious!

I think you can get this sound mostly through some OSCs and a lowpass filter, like you suggest. Using an LFO to modulate the should give you exactly the same results as turning the knob if you ignore the variable speed your manual knob turning has. The trick would be to dial in the amplitude of the LFO and the set the initial value correctly, aka, if you are turning the knob from 20% - 80%, that is an amplitude of +/-30% around an initial value of 50.

I think there is a hollowness to the sound, so at least one OSC should be a Square / PWN, the other a Saw, I recon.

The sound is also slightly gritty. So perhaps the MS-20's filter with a bit of resonance gets you closer than the very clean sounding AL-1, though AL-1's drive might work too. Adding a guitar amp or tube IFX mixed partially wet in might also get you there.

The same LFO modulating cutoff frequency (AMS1) simultaneously with amplitude (tremolo effect) with a sine or triangle waveform,
A second LFO, with a square waveform and very slow speed, modulates abruptly cutoff frequency only (AMS2).

In the both cases, setting the Modulation Amounts would give the right result.
I would use Saw/Pulse Oscillator waveform in AL-1 with a narrow pulse width._________________Kronos 2 73, Studiologic Sledge 2, Yamaha P90, Soundcraft EFX12, JBL LSR308